Cannulas are used in ophthalmic surgical procedures, such as retinal detachment surgery, to aspirate fluids such as blood, aqueous humor, and infused balanced saline solutions. The cannulas are typically connected by PVC tubing to a machine induced vacuum source and the fluids are collected in a disposable cassette in the machine. For ophthalmic surgical procedures, it is important that the cannula tip be specially designed for the delicate eye area. Thus, for example, such cannula tips are typically formed with rounded, smooth edges. Cannulas have also been made with a tip formed from a transparent soft material such as silicone. The soft silicone tip helps prevent damage to the delicate tissue of the eye in the event of physical contact with the eye.
Retinal detachment is a serious eye condition that, if not treated early, may lead to impairment or loss of vision. The condition typically affects older individuals, individuals with myopia (near-sightedness) and individuals with relatives having retinal detachment. In some instances, a hard, solid blow to the eye has lead to retinal detachment. Further, individuals who have undergone cataract surgery have, in some cases, subsequently developed retinal detachment.
The retina is a fine layer of nerve cells that covers the inside back portion of the eye (FIG. 2). If the retina thins, one or more small tears or holes in the retina may result (FIG. 3), leading to retinal detachment (FIG. 4). More often, retinal detachment is caused by shrinkage of the vitreous. The vitreous is a clear, gel-like substance that fills the inside of the eye and is firmly attached to the retina in several places. As the vitreous shrinks, as a result of age, inflammation, injury or near-sightedness, it often separates from the retina and, in some cases, it may pull a piece of the retina away with it, leaving a tear or hole in the retina. If the retina tears or breaks, watery fluid from the vitreous may pass through the hole and flow between the retina and the back wall of the eye producing “subretinal” fluid. Over time, the flow of the vitreous fluid between the retina and the back of the eye separates the retina from the back of the eye and causes it to detach (FIG. 4).
There are several procedures available to treat retinal detachment. The severity of the detachment or tear in the retina typically determines which of the procedures should be performed.
If the retina is torn but there is little or no retinal detachment, laser photocoagulation may be used to seal the retinal tears. During laser photocoagulation a laser is used seal the tear. Using the laser, small burns are placed around the edges of the tear. This produces scar tissue that seals the edges of the tear and prevents vitreous fluid from flowing through the tear.
Freezing or “cryopexy” is another procedure that is used to treat retinal tears. According to this procedure, the back wall of the eye behind the tear is frozen to produce scar tissue. As with laser photocoagulation, the scar tissue seals the edges of the tear and prevents vitreous fluid from flowing through the tear.
If the flow of the vitreous fluid between the retina and the back of the eye has caused the retina to detach, more complicated surgical procedures are required. In general, the detached portion of the retina is pressed against the back wall of the eye. Any subretinal fluid that is present must be drained from under the retina to allow the retina to settle back onto the back wall of the eye. The tears may then be sealed by use of, e.g., lasers, freezing, or an electrically heated needle which create scar tissue and seals the tear.
In severe cases, it is sometimes necessary to use a technique called vitrectomy. During this procedure, the vitreous body is cut away from the retina and removed from the eye. The vitreous cavity may then be filled with air or gas to push the retina back against the wall of the eye. In time, clear fluid from the blood seeps into and permanently fills the vitreous cavity.
During an ophthalmic procedure (e.g. retinal tear, retinal detachment, vitreoretinal procedure), the tip of a cannula is generally used to press a detached portion of the retina against the back wall of the eye, to fill the vitreous cavity with air or gas, and to remove the subretinal fluids from under the retina to allow the retina to return to its anatomically correct position.
A disadvantage of conventional cannulas is that the soft material of the cannula tip is transparent and, thus, difficult for the surgeon to discriminate during use, particularly during the fluid/air exchange when visibility is compromised by bubbles and a significant change in the refractive media from fluid to air.
There is a need for improved devices, systems and methods for use of these devices and systems during ophthalmic procedures. In particular, there is a need for improved devices, systems and methods for use during ophthalmic procedures wherein the device is easier for a user to detect and, thus, provides safe and easy manipulation around the particularly delicate eye area.